Allergies and sensitivities are caused by an inappropriate reaction to harmless substances. The word "allergy" comes from the Greek allos, meaning "other". It was first used in 1906 to refer to an "altered reaction" in the body's immune system.

A "true allergy" is a reaction triggered by the immune system, however there are a vast number of symptoms or conditions caused by sensitivities that may or may not involve the immune system. With reactions involving food, a large percentage of the population believes they have allergies, yet fewer than 2% actually have true allergies. In fact, many suffer from undiagnosed food sensitivities or intolerances. The majority of patients who seek the AAT treatment do not have true allergies; their symptoms are likely to be caused by sensitivities with no immune involvement. Since there are few options for the treatment of sensitivities, other than avoidance, AAT provides a highly affective alternative. Symptoms caused by true allergies, however, also respond well to the treatment as the organs systems involved in the reaction are also addressed.

The use of the word "allergy" has become a generic term used by the public to describe allergies, sensitivities and intolerances.